Patent GB-1093734-A (GB)
Title: A process for the production of insulating coatings on electric conductors
IPC: C08G73/16
Filed: 1966-06-01
Abstract: An insulating coating for an electrical conductor is produced by coating the conductor with a solution in an organic solvent of a hardenable condensation product, which contains polybasic carboxylic acid radicals, polyhydric alcohol radicals, amide groups and 5-membered imide rings, and heating the coating.  The condensation product may be derived from a polycarboxylic acid containing a pair of ortho carbonyl groups or an anhydride threof and an amino-compound, there being 1-1.95 pairs of carbonyl groups of anhydride groups present per pair of amino-groups.  The amino-compound may be a polyamine, an aminoalcohol, aminophenol or aminocarboxylic acid.  A polyhydric phenol may also be present. Compounds specified include trimellitic, pyromellitic, mellitic, terephthalic, isophthalic, naphthalene - 2,6 - dicarboxylic, trimesic, m - and p-aminobenzoic, 5 - aminoisophthalic, and aminoacetic acids, their esters and anhydrides, bis(4 - aminophenyl)methane, bis(4 - aminophenyl)ether, aminophenol, ethanolamine, 2-amino - 2 -methyl - propanol, 2 - amino - 2-methylpropane - 1,3 - diol, tris(hydroxymethyl)amino ethane, ethylene and propylene glycols, bis[4(b  - hydroxyethoxy)phenyl]propane, dimethylolcyclohexane, pentaerythritol, bisphenyl - A, hydroquinone, resorcinol, phenolphthalein, glycerol and trimethylol propane. The condensation may take place at 100-300 DEG  C. in the presence of a solvent and a catalyst.  A polyhydric alcohol or low m.p. polyester may simultaneously act as solvent and reactant. Solvents specified include cresol, a polyester produced from ethylene glycol, glycerol and terephthalic acid in the presence of zinc acetate and cresol (Examples 3, 4), a polyester prepared from ethylene glycol and trimesic acid in the presence of zinc acetate and cresol (Example 6) and a polyesteramide prepared from 5-aminoisophthalic acid and ethylene glycol in the presence of zinc acetate and cresol (Example 5).  Zinc acetate is specified as catalyst. After condensation the eliminated water and any excess polyhydric alcohol may be distilled out at up to 300 DEG  C. Solvents for the coating composition specified include cresol, naphtha, tetralin, xylene, propylene glycol, diacetone alcohol and ethylene glycol mono methyl ether monoacetate.  The coating composition may contain a catalyst, e.g. polymeric butyl titanates. It may be hardened at 300-500 DEG  C.ALSO:Insulating coatings on electrical conductors are produced by coating them with a solution of a hardenable polyester-amide-imide which contains in the molecule radicals derived from an acid having at least 3 carboxyl groups, two of which are on adjacent carbon atoms, radicals derived from a polyhydric alcohol and radicals derived from an amino compound having one amino group and at least one other amino, hydroxyl or carboxyl group, in the presence of an organic solvent, the coating being hardened by heating, wherein at least some of the amino groups co-condensed are in the form of amide bonds and the number of amide bonds does not exceed the number of five-membered imide rings.  A polyhydric phenol may also be present.  Polyfunctional carboxylic acids specified include: trimellitic, pyromellitic and mellitic. Other acids which may be present include terephthalic, isophthalic, naphthalene-2, 6-dicarboxylic and trimesic.  Polyhydric alcohols and phenols specified include: ethylene glycol, propylene glycol, bis[4(b -hydroxyethoxy)phenyl] propane, dimethylol cyclohexane, pentaerythritol, bisphenol-A, hydroquinone, resorcinol, phenolphthalein, glycerol and trimethylol propane.  Amino compounds specified include aminobenzoic acid, 5-amino-isophthalic acid, aminoacetic acid, bis(4-aminophenyl)methane, bis(4 - aminophenyl)ether, aminophenol, ethanolamine, 2-amino-2-methylpropane-1,3-diol and tris(hydroxymethyl)amino -ethane.  Solvents specified include cresol, naphtha, tetralin, xylene, propylene glycol, diacetone alcohol and ethylene glycol monomethyl ether mono acetate.  The composition is applied to copper wires and hardened at 300-500 DEG C using a polymeric butyl titanate as catalyst.